[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at dc67340 [CMake] Remove -Wl,-allow-shlib-undefined which was added in rL221530
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   dc67340..b21ddde  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to b21ddded8f04fee925bbf9e6458347104b5b99eb.
CMake Error at CMakeLists.txt:3 (cmake_minimum_required):
  CMake 3.13.4 or higher is required.  You are running version 3.7.1


-- Configuring incomplete, errors occurred!